In the months before the Parkland school mass shooting, several people told authorities they were concerned about Nikolas Cruz’s propensity for violence but none of those red flags prevented him from holding onto the cache of guns he already owned.

This week, Florida’s Legislature is voting on “red flag” or “risk warrant” legislation that would give police officers the power to temporarily remove guns and ammunition from people who show warning signs of violence to themselves or others. Supporters say the measures can save lives by reducing the number of shootings and suicides.

Sen. Marco Rubio said he plans to introduce similar federal legislation that would give “law enforcement and close family members” the ability to obtain a court order to prevent future gun sales or remove guns from individuals who may pose a threat.

Five states — California, Connecticut, Indiana, Oregon and Washington — already have laws that enable officers to remove firearms when they are notified about a person who has access to guns and may be a danger.

Their children died in the Feb. 14 mass shooting, and their goal now is persuading Florida legislators to pass laws that improve safety in schools.

“Our message is simple: We must be the last...

Police in Connecticut removed an average of seven guns from each person who had firearms seized, according to one independent academic study that analyzed the effectiveness of the state’s red flag law between 1999 and 2013.

Some other states are considering enacting similar laws, including Alaska, New York and Vermont. A bill in Alaska was introduced last year after Esteban Santiago, then an Anchorage resident, was arrested on federal charges he killed five people and injured six others in the Jan. 6, 2017, mass shooting at Fort Lauderdale-Hollywood International Airport. His trial is scheduled for June in federal court in Miami.

Two months before the shooting, Santiago, who had previously been accused of domestic violence, went to the FBI office in Anchorage and told agents that the government was trying to control his mind. A gun taken from his vehicle in the FBI parking lot was returned to Santiago by state authorities after he was hospitalized for a mental health evaluation.

The National Rifle Association did not respond to a request for comment on Florida’s proposed law. In the past, NRA lobbyists have said they think such laws can interfere with individuals’ Second Amendment rights to own guns, based on less evidence than would be required in criminal proceedings..

Connecticut, in 1999, was the first state to introduce such legislation one year after an employee fatally shot and stabbed four people at the state’s lottery headquarters, then took his own life.

Mike Lawlor, Connecticut’s current undersecretary for criminal justice policy and a former member of the state legislature, said that when he helped write and pass the law in 1999, he figured it would rarely be used.

But after the Virginia Tech massacre in 2007, Connecticut saw a significant increase in the number of people calling law enforcement to report concerns about troubled people with access to firearms. The number of “risk warrants” issued almost doubled from 26 in 2006 to 51 in 2007.

The numbers peaked after the 2012 Sandy Hook mass shooting at an elementary school in Newtown, Conn.: 183 gun confiscation orders were issued in the following year.

“Nobody picked up the phone and called police,” Lawlor said. “The shooter was not on law enforcement’s radar screen.”

To date, 1,519 orders have been issued — including 19 this year.

“I think people are more inclined to call the police now that we have seen more of these mass shootings in our country,” Lawlor said. “People say ‘I would never be able to live with myself if I hadn’t called.’ ”

Cruz, 19, a former student at Marjory Stoneman Douglas High School, used an AR-15 semiautomatic rifle that he legally purchased about a year before the massacre, investigators said.

The proposed law in Florida — a response to the shooting at Marjory Stoneman Douglas High School — is part of a wide-ranging Senate bill that would allow some school employees to carry guns, increase the age to buy firearms and provide millions of dollars for school safety improvements and mental health programs. The “red flag” provision was not included in the House version of the bill as of Monday.

The proposal is similar to legislation already in place in a few other states. The laws are sometimes called “extreme risk protection orders” and give police a non-criminal way to seize firearms. The laws allow police to remove guns from a person who is distressed or making threats.

Supporters say the process respects individuals’ constitutional rights by creating a civil court procedure for law enforcement to obtain a court order that would temporarily bar a person from having access to firearms and ammunition.

Jeffrey Swanson,who co-authored the study on Connecticut’s law, said research showed the legislation appears to be effective in reducing suicides. Proving its effect on mass shootings would be much more challenging, he said, because mass shootings are statistically much rarer than suicides. That means there is a much smaller pool of examples to study.

Gun-safety laws have to address the wide range of issues involved, said Swanson, a professor of psychiatry and behavioral sciences at Duke University in Durham, N.C.

Gun-removal laws close loopholes in existing legislation and give police officers a way to legally remove guns in a way that respects constitutional rights, he said.

Police have to prove there is sufficient evidence to support their request and a judge — in civil, not criminal, court — makes the final decision on whether the removal is legally justified. Police would also have to go back to court if they wanted to extended the period of confiscation of guns.

“If you prevent someone in crisis from purchasing a gun but they already have 12 other guns at home, that’s not going to stop them,” Swanson said.